Effects of free-cutting additives on the machinability of austenitic stainless steels

Experiments conducted to determine the effects of free-cutting additives on the machinability of austenitic stainless steel are described. Work materials were SUS303, SUS303Cu, SUS304 and SUS316, the contents of the additives, such as S, Ca, Cu and Bi, were varied and the steels were melted in furnaces of a commercial scale and a vacuum induction furnace were used. Machining tests were carried out dry and with a cutting fluid on an NC lathe using K10 carbide tools. The following cutting conditions were chosen in consideration of finish turning of parts for electronic appliances: a feed rate of 0.05–0.1 mm/rev and a cutting speed range of 12.5–100 m/min. The usual measurements were made and microhardness in the machined surface layer and strain-induced martensitic transformation were also measured. The machinability was evaluated especially in terms of the integrity of the machined surface.